dougettinger wrote:Indeed, an electron is a particle with some mass as is proven by collisions witnessed in a bubble chamber.
By that test, every particle has a mass. The mass of the electron was measured by suspending tiny particles in an electric field, offsetting gravity.
So what is a typical velocity of an electron traveling in an orbital cloud around an atomic nucleus based on the Bohr model using a balance of electrostatic and centripetal forces ?
There is no electron cloud in the Bohr model. In that model the electron's position and velocity are deterministic.
I always thought the orbital cloud represented the uncertainty of locating the electrons' positions; It would be comparable to looking at the solar system from a far distant external position and trying to locate accurately the position of a planet with all its perturbations, elliptical precessions, possible collisions/ejections, inclination changes, etc. over large periods of time ( because in the time period that a person tries to observe an electron it has more than likely orbited the nucleus millions or billions of times).
The cloud describes a physical region where the electrons are likely to exist. At the quantum level, the electrons have no fixed, describable position. The orbital is a function that describes the probability of an electron being in a particular region. Unlike the Solar System, the regions described by orbitals are not orbits. That is, electrons do not travel in circular or elliptical paths around the atomic nucleus, and they do not have any velocity in a meaningful physical sense.
The Wikipedia article about the Bohr model
provides the necessary formula to calculate the velocity of electrons in orbit. But keep in mind that the model is non-physical, so these velocities don't represent what actual electrons are doing in an actual atom.